Intermetallic compound catalyst and method for preparing the same

Abstract

An intermetallic compound catalyst and a method of preparing the same are provided. The method includes forming core-shell particles including a transition metal oxide coating by irradiating ultrasound to a precursor mixture solution including a noble metal precursor, a transition metal precursor, and a support; forming intermetallic compound particles including a transition metal oxide coating by annealing the core-shell particles; and removing the transition metal oxide coating from the intermetallic compound particles.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0005700, filed on January 15, 2021, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to an intermetallic compound catalyst for a fuel cell and a method for preparing the same. BACKGROUND

[0004] A fuel cell is an energy conversion device that directly converts the chemical energy of a fuel into electrical energy. Compared to existing internal combustion engines, a fuel cell has higher efficiency and is a next-generation energy source that is attracting attention due to its high energy density and environmental friendliness.

[0005] Polyelectrolyte fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) mainly operate at low temperatures of less than or equal to about 80°C, and thus require electrode catalysts to increase the oxidation and reduction reaction rates of the fuel cell. In particular, platinum is mainly used as an electrode catalyst for a fuel cell because it is the only catalyst that can promote fuel (hydrogen or alcohol) oxidation and oxygen reduction from room temperature to about 100°C. However, since platinum is limited in reserves and is very expensive, it is very important to reduce the amount of platinum used or to maximize the catalytic activity per unit mass for the commercialization of a fuel cell.

[0006] In order to achieve the above-mentioned purpose, research on platinum alloy catalysts is being conducted. Platinum alloy catalysts have theoretically higher activity and stability than pure platinum catalysts due to the electrical and structural properties of the particle surface, and thus are attracting attention as a reliable alternative to fuel cell electrode materials.

[0007] In general, a platinum alloy catalyst is prepared by depositing a transition metal precursor with a starting material for a platinum catalyst, and then annealing it at a temperature of 700°C to 1200°C using a gaseous reducing agent such as hydrogen. However, this high-temperature annealing process increases the size of the alloy particles, thereby reducing the catalytic activity.

[0008] Accordingly, in the related art, a method for preparing an alloy catalyst without a high-temperature annealing process, such as a chemical reduction method, a carbonyl complex process, a microemulsion method, and a polyol method, has been studied. However, the alloy catalyst prepared by the above-mentioned methods has the following problems: a large amount of transition metals exist on the particle surface without forming an alloy, and these transition metals are easily melted during the operation of a fuel cell, thereby reducing durability and catalytic activity.

[0009] Accordingly, in order to prepare an alloy catalyst satisfying high catalytic activity and durability to be used as a fuel cell catalyst, it is necessary to solve the problem of reduction in performance and durability caused by elution of metal components and coarsening of particles. SUMMARY

[0010] In preferred aspects, a method of preparing an intermetallic compound catalyst is provided that is capable of improving catalyst performance and durability by maximizing the proportion of maintaining the ordered atomic arrangement of intermetallic compound particles and controlling the crystallinity of individual particles to suppress elution of metal components and coarsening of particles of the alloy catalyst.

[0011] In one aspect, a method of preparing an intermetallic compound catalyst is provided that includes: forming core-shell particles including a transition metal oxide coating; forming intermetallic compound particles including the transition metal oxide coating by annealing the core-shell particles; and removing the transition metal oxide coating from the intermetallic compound particles.

[0012] The term "intermetallic compound" or "intermetallic compound alloy" as used herein generally refers to a metallic compound or metallic alloy compound having a specific chemical formula formed by ionic or covalent bonds and containing a very limited number of fixed or variable metals (e.g., metal atoms). In certain preferred aspects, the intermetallic compound or intermetallic compound alloy can form a specific crystal structure, for example, by placing a specific single element in a specific position in the crystal structure, such that the intermetallic compounds can have a high melting point or high temperature resistance, but have low ductility. In certain aspects, this property can be different from a conventional (or non-intermetallic compound) metal alloy, which can be formed of an unordered solid solution of one or more metal elements and does not have a specific chemical formula or crystal structure. An exemplary intermetallic compound or intermetallic compound alloy can include one or more metals selected from cobalt (Co), iron (Fe), nickel (Ni), zinc (Zn), tin (Sn), manganese (Mn), copper (Cu), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), yttrium (Y), niobium (Nb), and alloys thereof.

[0013] Preferably, the core-shell particles can be formed by irradiating ultrasonic waves to a precursor mixture solution including a noble metal precursor, a transition metal precursor, and a support.

[0014] Preferably, the annealing can be performed at a temperature of about 800°C to about 1400°C.

[0015] The annealing can be performed for about 2 hours to about 10 hours.

[0016] The core-shell particles can include a transition metal core, a noble metal shell surrounding the transition metal core, and a transition metal oxide coating layer surrounding the noble metal shell.

[0017] The transition metal oxide coating can include Fe2O3.

[0018] The transition metal oxide coating can have a thickness of about 0.2 nm to about 0.88 nm.

[0019] The irradiation of the ultrasound can be performed at an output of about 125 W to about 200 W for about 20 minutes to about 4 hours, based on a 100 mL precursor mixture solution.

[0020] The annealing can be performed under a mixed gas including hydrogen (H2) and argon (Ar), which can include hydrogen (H2) in an amount of about 1 vol% to about 10 vol% based on the total volume of the mixed gas.

[0021] The removing of the transition metal oxide coating from the intermetallic compound particles can be performed by acid treatment.

[0022] The acid treatment can be performed at a temperature of about 60 °C to about 94 °C for about 2 hours to about 4 hours.

[0023] The acid used for the acid treatment can include HCIO4, HNO3, HC1, or a combination thereof.

[0024] The acid can have a concentration of about 0.01 M to about 1.0 M.

[0025] The intermetallic compound catalyst can include an intermetallic compound core of a transition metal and a noble metal, and a noble metal surface layer surrounding the intermetallic compound core.

[0026] The intermetallic compound core can have an atomic arrangement order degree greater than or equal to about 58%.

[0027] The method of preparing the intermetallic compound catalyst according to various exemplary embodiments described herein can improve catalyst performance and durability by maximizing the proportion of maintaining the ordered atomic arrangement of the intermetallic compound particles and controlling the crystallinity of individual particles to suppress the elution of metal components and the coarsening of particles.

[0028] Other aspects of the present application are disclosed infra. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 An exemplary method of preparing an exemplary intermetallic compound catalyst according to exemplary embodiments of the present application is illustrated.

[0030] Figure 2 Results of in-situ XRD analysis of intermetallic compound catalysts prepared in Comparative Examples are illustrated.

[0031] Figure 3Measurement results of atomic arrangement order degree of intermetallic compound catalysts prepared in Examples and Comparative Examples.

[0032] Figure 4 Phase transition diagram of intermetallic compound catalyst prepared in Comparative Example.

[0033] Figure 5 Ideal XRD pattern of intermetallic compound PtFe catalyst.

[0034] Figure 6 Calculation results of ideal atomic arrangement order degree of intermetallic compound PtFe catalyst.

[0035] Figure 7 In-situ XRD analysis results according to annealing time variation in Examples.

[0036] Figures 8 to 10 XRD pattern and calculation results of atomic arrangement order degree according to annealing time variation in Examples.

[0037] Figure 11 In-situ XRD analysis results according to annealing temperature variation in Examples.

[0038] Figures 12 to 14 XRD pattern and calculation results of atomic arrangement order degree according to annealing temperature variation in Examples.

[0039] Reference numeral description

[0040] 10: Precursor mixture solution

[0041] 20: Core-shell particle

[0042] 30: Intermetallic compound catalyst

[0043] 110: Transition metal core

[0044] 120: Noble metal shell

[0045] 130: Intermetallic compound particle

[0046] 150: Transition metal oxide coating

[0047] 210: Intermetallic compound core

[0048] 220: Noble metal surface layer. DETAILED DESCRIPTION

[0049] Advantages and features of the present disclosure and implementations thereof will become apparent from the embodiments described hereinbelow and the accompanying drawings. Embodiments are not, however, to be construed as limited to the embodiments set forth herein. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Furthermore, no term is intended to be interpreted as having the broadest possible meaning or meaning to avoid defining specific embodiments. Finally, as used herein, the articles "a" and "an" are intended to include one or more items, and can be used interchangeably with "one or more." Unless otherwise noted, the terms "first," "second," and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Unless otherwise indicated herein, the use of the following terms herein, such as in the contexts of the description, the examples, and the appended claims, shall have the meanings set forth below and not the broader meanings that they can possess.

[0050] Unless otherwise indicated, in all cases, all numbers, values and / or expressions regarding amounts of ingredients, reaction conditions, polymer compositions and formulations used herein are to be understood to be modified by the term "about" as such numbers are inherent approximations due to, among other things, various measurement uncertainties.

[0051] Further, unless otherwise specifically stated or clearly contradicted by context, the term "about" as used herein is understood as within the normal tolerances of the art, for example within two standard deviations of the mean. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context clearly indicates otherwise, all numerical values provided herein are modified by the term "about."

[0052] In this specification, when describing ranges of variables, it will be understood that the variable includes all values, including the endpoints described in the range. For example, the range "5 to 10" will be understood to include any sub-range (e.g., 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc.) as well as the individual values 5, 6, 7, 8, 9, and 10, and will also be understood to include any value between the valid integers within the range, e.g., 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, etc. Additionally, for example, the range "10% to 30%" will be understood to include sub-ranges (e.g., 10% to 15%, 12% to 18%, 20% to 30%, etc.) as well as all integers (including 10%, 11%, 12%, 13%, etc. up to the value of 30%), and will also be understood to include any value between the valid integers within the range, e.g., 10.5%, 15.5%, 25.5%, etc.

[0053] Furthermore, the singular includes the plural, unless otherwise indicated.

[0054] A method of preparing an intermetallic compound catalyst includes: irradiating a precursor mixture solution with ultrasound to form core-shell particles including a transition metal oxide coating; annealing the core-shell particles to form intermetallic compound particles including the transition metal oxide coating; and removing the transition metal oxide coating from the intermetallic compound particles.

[0055] Figure 1 An exemplary method of preparing an intermetallic compound catalyst according to an exemplary embodiment of the present application is illustrated. As shown in Figure 1 A method of preparing an intermetallic compound catalyst is described.

[0056] Core-shell particles 20 including a transition metal oxide coating 150 are formed by irradiating a precursor mixture solution 10 including a noble metal precursor, a transition metal precursor, and a support with ultrasound (S1).

[0057] High frequency oscillation of ultrasound generates bubbles in a cavitation manner, so that the oscillation grows, and when the oscillation finally reaches a certain level, cavitation explosion occurs. This series of processes caused by ultrasound irradiation is called "sonic cavitation mechanism".

[0058] Cavitation explosion occurring in the final stage of the sonic cavitation mechanism generates a large amount of heat energy up to about 5000K, which is dissipated in a very short time of about 10 -6 seconds.

[0059] When the chemical reaction combines reactants for ultrasound irradiation of at least two materials having different vapor pressures, the rate at which at least two reactants evaporate into bubbles under the action of high frequency oscillation of ultrasound is different, so that the structure and electrochemical properties of the reaction product can be controlled using it. For example, when a nanoparticle containing at least two metals is prepared by using a noble metal precursor and a transition metal precursor as reactants and irradiating them with ultrasound, the distribution of noble metal and transition metal elements in the nanoparticle can be controlled according to the difference in vapor pressure of the noble metal precursor and the transition metal precursor.

[0060] For example, in a nanoparticle, a noble metal having a low vapor pressure can be disposed in a shell portion, and a transition metal having a high vapor pressure can be disposed in a core portion, thereby forming core-shell particles 20.

[0061] Irradiation of ultrasound can be performed at an output of about 125W to about 200W for about 20 minutes to about 4 hours based on 100mL of the precursor mixture solution 10. When irradiation of ultrasound is performed at an output of less than about 125W or for a time of less than about 20 minutes, metal ions cannot be sufficiently reduced; whereas when it is performed at more than about 200W or for more than about 4 hours, they grow to an unnecessary particle size.

[0062] The noble metal can include platinum (Pt), ruthenium (Ru), osmium (Os), iridium (Ir), palladium (Pd), alloys thereof, or mixtures thereof. The noble metal precursor can include those noble metal precursors having a vapor pressure lower than that of the transition metal precursor and facilitating the electrosubstitution reaction after the formation of the transition metal seed particles and the enlargement of their size. For example, the noble metal precursor can be in the form of a noble metal salt and can include a nitrate, a sulfate, an acetate, a chloride, an oxide, or a combination thereof. Preferably, the noble metal precursor can be an acetylacetonate of the noble metal, a hexafluoroacetylacetonate of the noble metal, or a pentafluoroacetylacetonate of the noble metal.

[0063] The transition metal can be cobalt (Co), iron (Fe), nickel (Ni), zinc (Zn), tin (Sn), manganese (Mn), copper (Cu), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), yttrium (Y), niobium (Nb), alloys thereof, or mixtures thereof.

[0064] The transition metal precursor can be in the form of a transition metal salt and can include, for example, a nitrate, a sulfate, an acetate, a chloride, an oxide, or a combination thereof. Preferably, the transition metal precursor can be an acetylacetonate of the transition metal, a hexafluoroacetylacetonate of the transition metal, or a pentafluoroacetylacetonate of the transition metal.

[0065] The transition metal precursor is rapidly volatilized under the effect of high vapor pressure and is rapidly captured in a cavitation manner under the effect of ultrasound, thus enabling the transition metal to be disposed in the core portion of the core-shell particle 20.

[0066] The support can be a carbon support, such as carbon black, graphite, carbon nanofiber, graphitized carbon nanofiber, carbon nanotube, carbon nanohorn, carbon nanowire, or a combination thereof. The carbon black can include denka carbon black, ketjen carbon black, acetylene carbon black, channel black, furnace black, lamp black, thermal black, or a combination thereof.

[0067] The precursor mixture solution 10 can further include a reducing solvent.

[0068] The reducing solvent can include an organic material free of moisture or oxygen source, such as a solvent having a reducing ability at a temperature greater than or equal to about 70 °C or a solvent having a reducing ability at a temperature of about 70 °C to about 400 °C. Preferably, the reducing solvent includes ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerol, or a combination thereof.

[0069] The reducing solvent functions to reduce the reactants of the noble metal precursor and the transition metal precursor formed in a cavitation manner by the ultrasonic treatment, and also maintains a high boiling point to create an external liquid environment for the generation and elimination of cavitation.

[0070] Meanwhile, on the surface of the core-shell particle 20 formed by the ultrasonic treatment, a transition metal oxide coating layer 150 surrounding the noble metal shell 120 can be included.

[0071] The transition metal oxide coating layer 150 can be formed by the insufficient dissolution of the transition metal in the platinum lattice, the difference in the reduction rate, and the composition ratio of the excess transition metal during the ultrasonic treatment.

[0072] The transition metal oxide coating layer 150 can have a thickness of about 0.2 nm to about 0.88 nm. When the thickness of the transition metal oxide coating layer 150 is less than about 0.2 nm, the transition metal oxide coating layer 150 is formed in a non-uniform and thin thickness, so that the particle size cannot be well controlled; and when the thickness is greater than about 0.88 nm, crystalline transition metal oxides are generated after annealing processing, leaving residues.

[0073] The transition metal oxide coating layer 150 is derived from a transition metal precursor as in the transition metal core 110, so the transition metal included in the transition metal oxide coating layer 150 can be the same as the transition metal included in the transition metal core 110.

[0074] For example, the transition metal oxide coating layer 150 can include Fe2O3. Since Fe2O3 has a thermal conductivity of about 20% (i.e., thermal conductivity of MgO: 35 W / m·K, thermal conductivity of Fe2O3: 7 W / m·K) compared to the case where the transition metal oxide coating layer 150 is not included or the case where the transition metal oxide coating layer 150 includes MgO, a difference in effective heat transfer rate occurs, so that when Fe2O3 is used, the intermetallic compound ratio can be increased without generating an order-disorder transition even at a high temperature annealing.

[0075] The method of preparing the intermetallic compound catalyst 30 according to the embodiment provides the core-shell particle 20 including the transition metal oxide coating layer 150 in one process using ultrasonic treatment, so that the process can be simplified to save costs.

[0076] The core-shell particle 20 is then annealed to provide an intermetallic compound particle including the transition metal oxide coating layer 150 (S2).

[0077] The atoms of the noble metal and the transition metal are regularly arranged by the annealing process, and the ratio of the transition metal core 110 decreases, thereby preparing the intermetallic compound particle 130. The intermetallic compound particle is an alloy of the noble metal and the transition metal, which is an intermetallic compound alloy in which the atoms of the noble metal and the transition metal are regularly arranged.

[0078] Since the transition metal oxide coating 150 inhibits the growth of particles, the size of the intermetallic compound particles 130 can be controlled to a size of several nanometers in the annealing process, and thus the metal atoms in the alloy can be regularly arranged by annealing at a sufficiently high temperature, thereby improving the uniformity of the composition and the catalytic activity. In addition, when the transition metal oxide coating 150 contains Fe2O3 as described above, the proportion of the intermetallic compound can be increased without the occurrence of an order-disorder transition even in high-temperature annealing by an effective heat transfer rate different from that of the conventional.

[0079] The annealing process can be performed at about 800℃ to about 1400℃ for about 2 hours to about 10 hours. When the annealing temperature is less than about 800℃ or the annealing time is less than about 2 hours, the increase in catalytic activity is limited due to insufficient improvement in the regular arrangement of metal atoms in the alloy. When the annealing temperature is greater than about 1400℃ or the annealing time is greater than about 10 hours, the effect of inhibiting the growth of the particle size is reduced, thereby resulting in a decrease in catalytic activity.

[0080] The annealing process can be performed in an inert gas atmosphere (e.g., argon, nitrogen), or a mixed gas atmosphere of an inert gas and hydrogen (H2), and an atmosphere containing about 1% to about 10% by volume of hydrogen based on the total volume of the mixed gas.

[0081] Finally, the transition metal oxide coating 150 is removed from the intermetallic compound particles 130 (S3).

[0082] The removal of the transition metal oxide coating 150 from the intermetallic compound particles 130 can be performed by acid treatment.

[0083] The acid used for the acid treatment can include HCIO4, HNO3, HCl, or a combination thereof.

[0084] The concentration of the acid can be about 0.01M to about 1.0M. When the concentration of the acid is less than about 0.01M, etching is insufficient, and the acid treatment time is prolonged, and when the concentration of the acid is greater than about 1.0M, platinum is also dissolved.

[0085] The acid treatment can be performed at a temperature of about 60℃ to about 94℃ for about 2 hours to about 4 hours. When the acid treatment temperature is less than about 60℃ or the acid treatment time is less than 2 hours, etching is insufficient. When the acid treatment temperature is greater than about 94℃, boiling within the vessel is severe even with reflux, thereby causing a safety problem, and when the acid treatment time is greater than about 4 hours, the transition metal content does not change, which wastes processing time and cost.

[0086] The intermetallic compound catalyst 30 can include an intermetallic compound core 210 of a transition metal and a noble metal, and a noble metal surface layer 220 surrounding the intermetallic compound core 210.

[0087] According to the method of preparing the intermetallic compound catalyst 30, since the core-shell particle 20 formed by irradiation with ultrasonic waves contains a transition metal in the core, the intermetallic compound catalyst 30 obtained by annealing the core-shell particle 20 contains noble metal particles exposed on the outer surface of the catalyst to provide a noble metal surface layer 220 in which the noble metal particles are dispersed on the surface of the intermetallic compound catalyst 30 at a high density.

[0088] Generally, since the slurry preparation process for electrode formation is performed at a pH value of less than or equal to about 1, and the fuel cell operates in an acidic atmosphere, the transition metal in the alloy catalyst is easily eluted, and the eluted transition metal enters the ion exchange membrane, thereby increasing the membrane resistance. As a result, it can cause a decrease in the performance of the fuel cell.

[0089] However, by providing a transition metal-noble metal alloy having an order degree and including a noble metal surface layer 220 on the surface, the intermetallic compound catalyst 30 obtained by the method of preparing the intermetallic compound catalyst can further improve the binding energy between the transition metal and the noble metal, so that it can inhibit the elution of the transition metal, thereby solving the problem of a decrease in the performance of the fuel cell.

[0090] The thickness of the noble metal surface layer 220 can be less than or equal to about 0.5 nm, or can be about 0.2 nm to about 0.5 nm. When the thickness of the noble metal surface layer 220 is greater than about 0.5 nm, its surface structure is similar to that of the existing platinum catalyst, and thus the effect of improved performance caused by alloying is lost.

[0091] In the intermetallic compound catalyst 30, the atomic ratio of the noble metal and the transition metal can be about 1:0.2 to about 1:0.6. When the atomic ratio of the transition metal is less than about 0.2, the formation of the intermetallic compound structure can be insufficient, and when it is greater than about 0.6, the thickness of the noble metal surface layer 220 can be insufficient.

[0092] The particle size of the intermetallic compound catalyst 30 can be about 3.5 nm to about 20 nm. When the particle size of the intermetallic compound catalyst 30 is less than about 3.5 nm, the order of atomic arrangement can be insufficient, and when it is greater than about 20 nm, it can be insufficient to ensure the electrochemical specific surface area.

[0093] The intermetallic compound core can have an atomic arrangement order degree of greater than or equal to about 58%, for example, about 58% to about 99%. When the atomic arrangement order degree of the intermetallic compound core is less than about 58%, the performance and durability of the fuel cell can decrease due to the elution of the transition metal.

[0094] In one aspect, there is provided an electrode for a fuel cell, which includes an intermetallic compound catalyst 30 and an ionomer mixed with the intermetallic compound catalyst 30.

[0095] Further provided is a membrane electrode assembly, which includes an anode and a cathode facing each other and an ion exchange membrane between the anode and the cathode, wherein the anode, the cathode, or both are the aforementioned electrode.

[0096] Also provided is a fuel cell including the aforementioned membrane electrode assembly.

[0097] The electrode, the membrane electrode assembly, and the fuel cell are the same as the general electrode, the membrane electrode assembly, and the fuel cell, except that they include the aforementioned ternary alloy catalyst 30, and thus a detailed description thereof will be omitted.

[0098] Embodiments

[0099] Hereinafter, specific embodiments of the present application are described. However, the embodiments described below are for illustrative purposes only, and the scope of the present application is not limited thereto.

[0100] Preparation Example: Preparation of Intermetallic Compound Catalyst

[0101] Example

[0102] Pt(acac)2, Fe(acac)3, and a porous carbon support (Vulcan XC72) were added to ethylene glycol to thereby prepare a precursor mixture solution, and then 100 mL of the precursor mixture solution was subjected to ultrasonic irradiation using a Tip-type ultrasonic wave (Sonic & Materials, Model VC-500, amplitude 30%, 13 mm solid probe, 20 kHz) at an output of 150 W for 3 hours under an argon atmosphere, to thereby provide core-shell particles including a transition metal oxide coating layer.

[0103] At this time, the amounts of the noble metal precursor and the transition metal precursor were adjusted so that the atomic ratio of the noble metal and the transition metal could be 1:1.5.

[0104] The prepared core-shell particles were annealed under an H2 / Ar mixed gas atmosphere, to thereby provide intermetallic compound particles including a transition metal oxide coating layer. At this time, the annealing temperature was varied to be 800°C, 1000°C, 1200°C, and 1400°C, and the annealing time was varied to be 2 hours, 6 hours, and 10 hours.

[0105] The intermetallic compound particles were treated with a mixed solution of 0.1 M HCIO4 acid and ethanol at a temperature of 94°C for 4 hours, to thereby prepare an intermetallic compound catalyst.

[0106] Comparative Example

[0107] Intermetallic compound catalysts are prepared using commonly used polyol synthesis methods without introducing transition metal oxide coatings.

[0108] Specifically, Pt(acac)2, Fe(acac)3 and porous carbon support (Vulcan XC72) are added to ethylene glycol to prepare a precursor mixture solution, which is then annealed at various temperatures of 600℃, 650℃, 675℃, 715℃, 750℃ and 825℃ to obtain an intermetallic compound catalyst.

[0109] Experimental Example 1: XRD analysis based on the annealing temperature of the intermetallic compound catalyst prepared in the comparative example.

[0110] In-situ XRD analysis was performed on the intermetallic compound catalysts prepared in the comparative examples, and the results are shown in... Figure 2 Furthermore, the atomic arrangement order of the intermetallic compound catalysts prepared in the Examples and Comparative Examples was measured, and the results are shown in... Figure 3 middle. Figure 4 The phase transition diagrams of the intermetallic compound catalysts prepared in the comparative examples are shown.

[0111] In the comparative example, the effective heat transfer rate is much faster than in the example because the annealing gas directly transfers heat in the method for preparing intermetallic compound particles without introducing a coating for controlling particle size.

[0112] As in Figure 2 As shown, when the temperature is increased, the intermetallic compound structure is maintained in the XRD pattern at temperatures from 32°C to 750°C by the presence of the (110) crystal plane peak, but the intermetallic compound structure reforms into a disordered structure at a temperature of 825°C.

[0113] As in Figure 3 As shown, in the comparative example, the proportion of intermetallic compounds increased (and then converged to 0) up to a temperature of 750°C, at which point the proportion of intermetallic compounds was 30%. Furthermore, reference is also made to… Figure 4 The phase transition diagram, during the theoretical verification process based on 5.2 nm, showed a transition from L12 (intermetallic compound) to DO at a temperature of approximately 700 °C. 22 Phase transition diagram of (disordered alloy). On the other hand, the proportion of intermetallic compounds increases continuously up to 1200°C, reaching almost 99%.

[0114] Experimental Example 2: XRD analysis of the intermetallic compound catalyst prepared according to the time and annealing temperature in the examples.

[0115] Figure 5Figure showing the ideal XRD pattern of the intermetallic compound PtFe catalyst with a size of 5.2 nm, Figure 6 Figure showing the calculation results of the ideal atomic arrangement order degree of the intermetallic compound PtFe catalyst.

[0116] In Figure 6 , P1, P3, P4, P6, P7 and P8 represent the intensity at the predetermined peak in the XRD pattern, and Table 1 shows the meaning of each peak. The atomic arrangement order degree of the intermetallic compound PtFe catalyst can be obtained by calculating (P1+P3+P7+P8) / (P4+P6), as shown in Figure 6 , the ideal atomic arrangement order degree of the intermetallic compound PtFe catalyst is about 0.31. Therefore, the atomic arrangement order degree of the prepared intermetallic compound PtFe catalyst can be measured by XRD, calculating (P1+P3+P7+P8) / (P4+P6), and calculating the ratio with respect to the ideal atomic arrangement order degree.

[0117] Table 1

[0118] Peak term Peak index Notes P1 001 PtFe P2 002 C P3 110 PtFe P4 111 PtFe P5 100 C P6 200 PtFe P7 002 PtFe P8 201 PtFe

[0119] Figure 7 Figure showing the in-situ XRD analysis results when the annealing temperature is set to 800°C and the annealing time is 2 hours, 6 hours and 10 hours; Figures 8 to 10 Figures showing the XRD pattern and the calculation results of the atomic arrangement order degree for the cases of annealing time of 2 hours, 6 hours and 10 hours, respectively, and Table 2 summarizes these results.

[0120] Table 2

[0121]

[0122] From Figures 7 to 10 and Table 2, in the case of the intermetallic compound PtFe catalyst obtained by changing the time (2 hours to 6 hours) under the same temperature condition (800°C), the atomic arrangement order degree (IM DoO) of the intermetallic compound did not change significantly, and in the case of 10 hours, it increased.

[0123] Meanwhile, Figure 11 Figure showing the in-situ XRD analysis results of the example when the annealing time is fixed to 2 hours and the annealing temperature is changed to 800°C, 1000°C, 1200°C, 1400°C; Figures 12 to 14 Figures showing the XRD pattern and the calculation results of the atomic arrangement order degree for the cases of annealing temperature of 800°C, 1000°C and 1200°C, respectively, and Table 3 summarizes these results.

[0124] Table 3

[0125]

[0126] As in Figures 11 to 14 As shown in Table 3, in the case of intermetallic compound PtFe catalysts obtained by temperature variation under the same annealing time conditions (2 hours), the atomic arrangement order (IM DoO) of the intermetallic compound changes significantly with temperature.

[0127] Specifically, samples annealed at temperatures between 800°C and 1200°C showed an increase in atomic arrangement order of approximately 5 nm in particle size, particularly at 1200°C, where the atomic arrangement order reached approximately 99%. Meanwhile, when annealed at 1400°C, the particle size increased to approximately 10 nm.

[0128] Although the invention has been described in conjunction with exemplary embodiments which are now considered practical, it should be understood that the invention is not limited to the disclosed embodiments, but rather is intended to cover various variations and equivalent arrangements that are included within the spirit and scope of the appended claims.

Claims

1. A method for preparing an intermetallic compound catalyst, comprising: Formation of core-shell particles including a transition metal oxide coating; Intermetallic compound particles, including a transition metal oxide coating, are formed by annealing the core-shell particles. as well as Remove the transition metal oxide coating from the intermetallic compound particles. The core-shell particles include: transition metal core, A precious metal shell surrounding the transition metal core, and A transition metal oxide coating surrounds the noble metal shell, the transition metal oxide coating comprising Fe2O3.

2. The method for preparing intermetallic compound catalysts according to claim 1, wherein, The core-shell particles are formed by irradiating a precursor mixture solution containing a noble metal precursor, a transition metal precursor, and a carrier with ultrasound.

3. The method for preparing intermetallic compound catalysts according to claim 1, wherein, Annealing is performed at temperatures ranging from 800°C to 1400°C.

4. The method for preparing intermetallic compound catalysts according to claim 1, wherein, Annealing takes 2 to 10 hours.

5. The method for preparing intermetallic compound catalysts according to claim 1, wherein, The thickness of the transition metal oxide coating is from 0.2 nm to 0.88 nm.

6. The method for preparing intermetallic compound catalysts according to claim 2, wherein, Based on a 100 mL precursor mixture solution, ultrasonic irradiation was performed for 20 minutes to 4 hours at an output of 125 W to 200 W.

7. The method for preparing intermetallic compound catalysts according to claim 1, wherein: Annealing was performed in a mixture of hydrogen and argon gases, and The mixed gas contains hydrogen in an amount of 1% to 10% by volume based on the total volume of the mixed gas.

8. The method for preparing intermetallic compound catalysts according to claim 1, wherein, The removal of transition metal oxide coatings from intermetallic compound particles is performed by acid treatment.

9. The method for preparing intermetallic compound catalysts according to claim 8, wherein, Acid treatment is carried out at a temperature of 60°C to 94°C for 2 to 4 hours.

10. The method for preparing an intermetallic compound catalyst according to claim 8, wherein, Acids used for acid treatment include HClO4, HNO3, HCl, or combinations thereof.

11. The method for preparing an intermetallic compound catalyst according to claim 8, wherein, The concentration of the acid is from 0.01M to 1.0M.

12. The method for preparing intermetallic compound catalysts according to claim 1, wherein: Intermetallic compound catalysts include: The intermetallic compound cores of transition metals and noble metals, and A noble metal surface that surrounds the intermetallic compound core.

13. The method for preparing an intermetallic compound catalyst according to claim 12, wherein, Intermetallic compounds have a nuclear arrangement order of 58% or more atoms.

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